In the treatment of tumors by irradiation with microwave radiation, the affected tissue is heated by the microwave radiation to an elevated temperature at which the tumor hopefully is killed while the healthy tissue survives.
It is of course critical to monitor the temperature of the tissue during this operation, since too low a temperature will be ineffective against the tumor, and too high a temperature will result in burning of healthy tissue. Thermocouples have been implanted into the tissue which is being irradiated by microwaves to assist in monitoring of the temperatures.
As is well-known, a microthermocouple may be made from a pair of wires of dissimilar metals. For example one wire may be made of copper while the other may be made of the commercially available Constantan alloy. The wires are joined together at one end, and their other ends are connected to a readout apparatus which may directly read out termperature if desired, for example, an apparatus manufactured by the Bailey Instrument Company or other commercially available units.
The thermocouple wires may then be implanted into the desired tissue with the thermocouple wires occupying a metal needle or the like, for measurement of the temperature.
However, the above techniques have resulted in inaccurate temperature readouts because the very presence of a relatively bulky intrusion as represented by the Teflon sheath or other prior art means for implanting the thermocouple can disturb the tissue microcirculation so that the temperature sensed by the thermocouple can be several degrees different from the actual tissue temperature. This is of course undesirable.
Also, tissue implantable thermocouples have utilized relatively large wires of dissimilar metal as has been previously necessary to prevent wire breakage. Relatively large wires having diameters in excess of about 75 microns can pick up significant amounts of the microwave radiation to heat, thus causing burns.
Similarly, thermocouples mounted on the ends of needles or stylets are undesirable because the needle or stylet can readily heat in the presence of microwave irradiation, contributing to burning of the tissue.
In accordance with this invention a microthermocouple member is provided, plus a method for implanting it, in which improved accuracy of temperature readout can be provided, and the wires may be sufficiently small in diameter so that their overheating and burning as the result of exposure to a microwave field is not a problem.
Furthermore, the microthermocouple member and method of this invention may be used in fields other than microwave therapy as may be desired by the user.